1. Field of the Invention
The present invention relates to a carborane compound, an organic light-emitting diode including the same, and a flat display device including the organic light-emitting diode.
2. Description of the Related Art
Organic light-emitting diodes (OLEDs), which are self-emitting devices, have advantages such as a wide viewing angle, excellent contrast, quick response, high brightness, and excellent driving voltage characteristics, and can provide multicolored images.
A general OLED has a structure including a substrate, and an anode, a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and a cathode which are sequentially stacked on the substrate. In this regard, the HTL, the EML, and the ETL are organic layers formed of organic compounds.
An operating principle of an OLED having the above-described structure is as follows. When a voltage is applied between the anode and the cathode, holes injected from the anode move to the EML via the HTL, and electrons injected from the cathode move to the EML via the ETL. The holes and electrons recombine in the EML to generate excitons. When the excitons drop from an excited state to a ground state, light is emitted.
Excitons generated by current excitation are divided into two types: singlet exciton and triplet exciton. The singlet exciton and the triplet exciton are formed at a ratio of 1 to 3 according to spin statistics theorem. In general, singlet excitons contribute to light emission in fluorescent materials, and triplet excitons contribute to light emission in phosphorescent materials. 25% of singlet exciton generation restricts the luminous efficiency of a fluorescent material.
In a case where triplet excitons contribute to luminescence, when a possibility of intersystem crossing (ISC) from a singlet state to a triplet state is high, luminous efficiency may be enhanced. Organometallic compounds including iridium (Ir), platinum (Pt), or the like have relatively high luminous efficiency because intersystem crossing occurs therein by heavy atomic effect.
However, there is a need to develop other materials with high luminous efficiency except for phosphorescent organometallic compounds.